24/11/05 - Article - The AS-i Diagnosis Tuner




New: The AS-i Diagnosis Tuner

Functions


The passive Tuner was introduced to the market by Bihl+Wiedemann one year ago and proved itself for (automatical) optimzation of AS-Interface networks (see box below). Now the second innovation step has brought out an advanced Tuner which plays as a slave an active part in communication with the PLC. So in addition to its primary task which is the circuit extension without repeater (up to 300 m), the Tuner becomes a diagnosis device which inform the PLC online about the quality of the bus function.


    In detail:
  1. The Tuner continually transmits the information displayed by its three LEDs green, yellow (warning), red (error) – to the PLC. So its global trafficlights display is now available in the PLC but not only somewhere in the plant.
  2. The result can be implemented in the application program. It signalizes if an optimization was achieved. Gradual changes of the AS-i network's quality which could lead to problems in the medium-term are recognized before they occure.
  3. The AS-i Diagnose Tuner can message the trafficlights display for every slave to the superordinated control. For this reason its diagnosis function rises above the diagnosis functions of the passive Tuner. So the user receives the information about the performance of the communication with every slave.
  4. The AS-i Diagnosis Tuner can measure the currrent AS-Interface voltage at the location of the Tuner and transfer it as a 16bit value to the PLC.
  5. The advanced Tuner stores the minimum voltage regarding the plant's – last switch-off (or its deletion). This value can be called by the PLC.
  6. The advanced Tuner can be activated to accomplish a new try for optimizing.
  7. The AS-i Diagnosis Tuner can be completely turned off via a switch or can be set to a default value.

Interoperable and downward compatible:

As well as the prevoius, passive tuner which works within every AS-Interface network – independent of the network's manufacturer – the advanced Tuner is interoperable in all its functions with every Master (Gateway, Link) and in every network. So it is always retrofit.
Since the AS-i Diagnosis Tuner needs the AS-i specification 3.0 for functions (3), (4) and (5), these functions can only be used in combination with an AS-i 3.0 Master. However all other functions are available with a specification 2.0 or 2.1 Master (Master Profiles M1 and M3) as well.

Info: Combi-Slave Profile

The Diagnosis Tuner operates according to the new "Combi-Slave-Profile" S 7.A.5 in which digital and serial data are transmitted in parallel. The 2I/1O for the Tuner's main functions are transmitted according to custom and can be used by every Master. The serial data - here the analog values of the voltage and the traffic lights values of the slaves – are transmitted piece by piece, then reassembled by the Master and from here they are sent to the PLC as a simple complete telegram. The user finds the currently measured AS-i voltage and the minimum AS-i voltage inside the field of the analog input data as a 16 bit analog value just as he is accustomed to the analog value transfer.
For this reason A/B transfer rates of approx. 50 bd are possible with AS-Interface. The Diagnosis Tuner's ID-Codes "A" makes it a slave with extended addressing. In A/B operation it has one of 62 addresses , in the standard mode as an A-slave it owns one of 31 addresses.

Benefits

If the diagnosis data is completely implemented in a user program the connected network can be continously observed in terms of telegram repetitions. Unless they appear too frequently those repetitions are harmless with AS-i. Mechanisms for error detection assure this reliably. In case the repetition's number increases and the application recognizes this, you can counteract e.g. within preventive maintenance at an early stage, long before a slave fails.
So this device does not only serve as a means for optimizing and extending the network but as a valuable diagnosis tool which helps to assure a long-run troublefree process.



Article as PDF file

The article appeared in SPS-Magazin, 18th volume, 12th issue

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